This invention relates to compost tea, also known as compost extract, and more particularly, to apparatus and methods for producing compost tea.
Compost teas are being used with increased frequency by both commercial agricultural enterprises and home gardeners for the many benefits they offer, such as control of root and foliar diseases via the action of beneficial microorganisms, and as a source that adds nutrients to plants and soil. Simply described, a compost tea is an aqueous extract of compost that is produced by extracting nutrients and microorganisms from compost. The extraction is often coupled with production aeration, agitation and microbial foods to increase the microbial density of the resulting extractxe2x80x94the tea. Some of the many benefits of compost teas have been recognized for many years. However, teas are becoming more and more recognized as important agricultural tools since they provide an alternative method of addressing such common agricultural concerns as disease control and nutrient supplementation. Among other benefits, compost tea generally provides an organic product that is economically manufactured and applied to crops and soil, and which allows the reduction or elimination of non-organic crop pesticides and fertilizers.
There are several known general methods of making compost teasxe2x80x94all of the methods rely upon high quality compost as a starting material to ensure a high quality extract. Various manufacturing techniques are used to leach a complex nutrient and microbiologically rich aqueous extract from the compost. The quality of the tea in terms of nutrient makeup and concentration and in terms of microbiological load and diversity depends to a large degree on the quality of the compost starting material, the food or nutrient package added to feed the microorganisms and on the method used to make the tea. Regardless of how it is made, liquid compost tea may be applied to plants in the form of a foliar spray, for instance to combat disease. Used in this way the tea provides an active method of controlling plant pathogens through mechanisms such as inhibition of spore germination, antagonism, and microbial competition with various plant pathogens. When applied as a spray, the tea also provides quickly usable nutritional supplements for the plant. Teas may also be applied directly to the soil to add nutrients to the soil and to increase the microbial density and diversity.
Given the complex microbial diversity found in high quality composts, and the rich nutrient makeup of composts, it is natural that compost teas have a similarly complex microbiological and macro, micro and trace element composition. The number and type of bacteria found in compost teas varies of course with many factors, including the bacterial species found in the starting compost, and the manner in which the tea is extracted. Thus, compost from a source such as animal manure will have a substantially different microbial load than compost derived from a plant origin, and a tea made from such composts will likewise have different microbial diversity. Nonetheless, and generally speaking, a high quality compost tea will be rich in aerobic bacteria, yeasts and fungi, as well as many varied nutrients. The methods of manufacturing the teas are designed to enhance the presence of such desirable components.
There are numerous methods of manufacturing compost teas, and the known methods involve both production of the liquid extract and aeration to ensure aerobic flora are selected and reproduce at a high rate. One of the simplest methods of making tea, and also one of the earliest reported methods involves covering compost with water, stirring the combination and allowing it to soak (and ferment) for a period of between 2 to 21 days. The liquid is then separated from particulate material by straining through cheesecloth and may be applied to crops and soil with ordinary spray equipment.
While this simple method produces an acceptable, low cost compost tea, it has been recognized that aerating the liquid to increase the concentration of dissolved oxygen in the liquid can enhance the growth of aerobic microorganisms and decrease tea production time production. One simple method of aeration is to create a trough by cutting a pipe in half lengthwise and drilling plural holes in the pipe to allow drainage. The pipe is laid on its side and is suspended over a tank. Compost is filled into bags such as burlap and laid in the trough. Water is then sprayed over the burlap. As the water filters through the compost it extracts nutrients and microbiological organisms. The water is circulated from the tank through the sprayers for several days. By spraying the liquid and by allowing it to drain through the trough the concentration of oxygen in the liquid increases, and this enhances the selection and growth of desirable aerobic microorganisms.
Not surprisingly, with the increased awareness that compost teas provide economical and organic alternatives to pesticides and fertilizers, more automated methods of manufacturing teas have been developed. These range from small devices that provide constant stirring and aeration of compost in water-filled tubs, to more complex devices such as the one described in U.S. Pat. No. 6,168,949. The xe2x80x9cbioreactorxe2x80x9d described in the ""949 patent uses a tank having a conical bottom that holds the production liquid. The liquid is circulated through the tank by pumping it through the bottom and spraying it through an atomizing nozzle in the headspace above the liquidxe2x80x94called a vortex chamber. The finely divided spray produced by the atomizing nozzle allows for the introduction of gases in the headspace into the liquidxe2x80x94oxygen for instance.
These known methods of making compost tea are useful for making the product. However, there is a need for a compost tea system that is simple and which allows for the manufacture of high quality teas. The present invention provides a compost tea production apparatus that is simply constructed and simple to operate, and which provides a high quality tea rich in aerobic bacteria.
The tea system of the present invention uses a production tank that is filled with water that does not recirculate the water through a pump. Compost is introduced into the liquid in filter baskets suspended in the tank. Oxygen is introduced into the liquid through membrane disk diffusers positioned on the bottom of the tank. As air is pumped into the diffusers it is bubbled through the liquid in fine bubbles that have a high surface area to volume ratio. This causes both passive circulation of the liquid to ensure a homogenous blend of nutrients and constant turnover of the liquid, and maintains the concentration of dissolved oxygen in the liquid at a high level to encourage growth of desired aerobic organisms during the production cycle production. The entire production process is accomplished relatively quickly with the system of the present invention, and high quality compost teas may be produced within 24 hours.